Conventionally, a carbon dioxide separation and recovery system which separates and recovers carbon dioxide from a target gas by use of a solid adsorbent is known. For example, Patent Literature 1 discloses a carbon dioxide separation and recovery system 100 as shown in FIG. 3.
Specifically, in the carbon dioxide separation and recovery system 100 an adsorbent is transferred to a hopper 110, an adsorption tower 120, a regeneration tower 130, a drying tower 140, and a cooling tower 150 in this order. Also, the adsorbent is returned from the cooling tower 150 to the hopper 110 by a conveyor 160.
In the adsorption tower 120, a target gas is caused to contact the adsorbent, and carbon dioxide contained in the target gas is adsorbed to the adsorbent. Steam is supplied from the drying tower 140 to the regeneration tower 130. This steam is condensed on the adsorbent having adsorbed the carbon dioxide, and thereby the carbon dioxide is desorbed from the adsorbent. The desorbed carbon dioxide is suctioned into a recovery pump 170 through a carbon dioxide recovery path 135, compressed by the recovery pump 170, and then reserved in a carbon dioxide holder 180.
The drying tower 140 evaporates the condensed water adhering to the adsorbent by indirect heating. The steam generated by evaporating the condensed water is supplied to the regeneration tower 130 as the steam used for regenerating the adsorbent. For example, saturated steam (e.g., 60 degrees C.) having a negative pressure (about 20 kPa in an absolute pressure) in a gauge pressure is supplied to the drying tower 140 as a heat medium.
The drying tower 140 and the regeneration tower 130 constitute a tank having a unitary (integrated) construction. Therefore, each of the interior of the drying tower 140 and the interior of the regeneration tower 130 is adjusted to have a pressure (e.g., about 20 kPa) in which the heat medium allows the condensed water to be evaporated, by the suction operation of the recovery pump 170. For this reason, differential pressure holding devices (e.g., lock hoppers) for holding pressure differences with respect to an atmospheric pressure are provided at a location between the adsorption tower 120 and the regeneration tower 130 and a location between the drying tower 140 and the cooling tower 150, respectively.